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   "source": [
    "# C++的关键字"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# 1. 关键字"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "① 关键字是C++中预先保留的单词(标识符)。\n",
    "\n",
    "② 在定义变量或者常量的时候，不要用关键字。"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 1.1 int关键字"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "#include <iostream>\n",
    "using namespace std;\n",
    "\n",
    "int main()\n",
    "{\n",
    "\n",
    "    // int int = 10;  // 错误，第二个int是关键字，不可以作为变量的名称\n",
    "\n",
    "    system(\"pause\");\n",
    "\n",
    "    return 0;\n",
    "\n",
    "}"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "运行结果：  \n",
    " - 请按任意键继续. . ."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 1.2 sizeof关键字"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "① sizeof关键字可以统计数据类型所占内存大小。\n",
    "\n",
    "② sizeof关键字，语法：sizeof ( 数据类型 / 变量 )"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "#include <iostream>\n",
    "using namespace std;\n",
    "\n",
    "int main()\n",
    "{\n",
    "\n",
    "    cout << \"short 类型所占内存空间为：\" << sizeof(short) << endl;\n",
    "\n",
    "    system(\"pause\");\n",
    "\n",
    "    return 0;\n",
    "\n",
    "}"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "运行结果：  \n",
    " - short 类型所占内存空间为：2  \n",
    " - 请按任意键继续. . ."
   ]
  }
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